[PATCH 09/26] KVM: x86: Calculate the supported xcr0 mask at load time

[Sean Christopherson]

Add a new global variable, supported_xcr0, to track which xcr0 bits can
be exposed to the guest instead of calculating the mask on every call.
The supported bits are constant for a given instance of KVM.

This paves the way toward eliminating the ->mpx_supported() call in
kvm_mpx_supported(), e.g. eliminates multiple retpolines in VMX's nested
VM-Enter path, and eventually toward eliminating ->mpx_supported()
altogether.

No functional change intended.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
 arch/x86/kvm/cpuid.c   | 15 ++-------------
 arch/x86/kvm/svm.c     |  2 ++
 arch/x86/kvm/vmx/vmx.c |  4 ++++
 arch/x86/kvm/x86.c     | 14 +++++++++++---
 arch/x86/kvm/x86.h     |  7 +------
 5 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index b1c469446b07..51b604c9a3f5 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -52,16 +52,6 @@ bool kvm_mpx_supported(void)
 }
 EXPORT_SYMBOL_GPL(kvm_mpx_supported);
 
-u64 kvm_supported_xcr0(void)
-{
-	u64 xcr0 = KVM_SUPPORTED_XCR0 & host_xcr0;
-
-	if (!kvm_mpx_supported())
-		xcr0 &= ~(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
-
-	return xcr0;
-}
-
 #define F feature_bit
 
 int kvm_update_cpuid(struct kvm_vcpu *vcpu)
@@ -107,8 +97,7 @@ int kvm_update_cpuid(struct kvm_vcpu *vcpu)
 		vcpu->arch.guest_xstate_size = XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET;
 	} else {
 		vcpu->arch.guest_supported_xcr0 =
-			(best->eax | ((u64)best->edx << 32)) &
-			kvm_supported_xcr0();
+			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
 		vcpu->arch.guest_xstate_size = best->ebx =
 			xstate_required_size(vcpu->arch.xcr0, false);
 	}
@@ -644,7 +633,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function,
 	}
 	case 0xd: {
 		int idx, i;
-		u64 supported = kvm_supported_xcr0();
+		u64 supported = supported_xcr0;
 
 		entry->eax &= supported;
 		entry->ebx = xstate_required_size(supported, false);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index df4d0b6f31c8..f3e6dcefc094 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1368,6 +1368,8 @@ static __init int svm_hardware_setup(void)
 
 	init_msrpm_offsets();
 
+	supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
+
 	if (boot_cpu_has(X86_FEATURE_NX))
 		kvm_enable_efer_bits(EFER_NX);
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index ed63219ca52e..f16c1faf6ced 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7620,6 +7620,10 @@ static __init int hardware_setup(void)
 		WARN_ONCE(host_bndcfgs, "KVM: BNDCFGS in host will be lost");
 	}
 
+	if (!kvm_mpx_supported())
+		supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS |
+				    XFEATURE_MASK_BNDCSR);
+
 	if (!cpu_has_vmx_vpid() || !cpu_has_vmx_invvpid() ||
 	    !(cpu_has_vmx_invvpid_single() || cpu_has_vmx_invvpid_global()))
 		enable_vpid = 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index adbdbe785f05..03e656d05c15 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -180,6 +180,11 @@ struct kvm_shared_msrs {
 static struct kvm_shared_msrs_global __read_mostly shared_msrs_global;
 static struct kvm_shared_msrs __percpu *shared_msrs;
 
+#define KVM_SUPPORTED_XCR0     (XFEATURE_MASK_FP | XFEATURE_MASK_SSE \
+				| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
+				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
+				| XFEATURE_MASK_PKRU)
+
 static u64 __read_mostly host_xss;
 
 struct kvm_stats_debugfs_item debugfs_entries[] = {
@@ -226,6 +231,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 };
 
 u64 __read_mostly host_xcr0;
+u64 __read_mostly supported_xcr0;
+EXPORT_SYMBOL_GPL(supported_xcr0);
 
 struct kmem_cache *x86_fpu_cache;
 EXPORT_SYMBOL_GPL(x86_fpu_cache);
@@ -4081,8 +4088,7 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu,
 		 * CPUID leaf 0xD, index 0, EDX:EAX.  This is for compatibility
 		 * with old userspace.
 		 */
-		if (xstate_bv & ~kvm_supported_xcr0() ||
-			mxcsr & ~mxcsr_feature_mask)
+		if (xstate_bv & ~supported_xcr0 || mxcsr & ~mxcsr_feature_mask)
 			return -EINVAL;
 		load_xsave(vcpu, (u8 *)guest_xsave->region);
 	} else {
@@ -7310,8 +7316,10 @@ int kvm_arch_init(void *opaque)
 
 	perf_register_guest_info_callbacks(&kvm_guest_cbs);
 
-	if (boot_cpu_has(X86_FEATURE_XSAVE))
+	if (boot_cpu_has(X86_FEATURE_XSAVE)) {
 		host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
+		supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0;
+	}
 
 	kvm_lapic_init();
 	if (pi_inject_timer == -1)
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 3624665acee4..02b49ee49e24 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -280,13 +280,8 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 			    int emulation_type, void *insn, int insn_len);
 enum exit_fastpath_completion handle_fastpath_set_msr_irqoff(struct kvm_vcpu *vcpu);
 
-#define KVM_SUPPORTED_XCR0     (XFEATURE_MASK_FP | XFEATURE_MASK_SSE \
-				| XFEATURE_MASK_YMM | XFEATURE_MASK_BNDREGS \
-				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
-				| XFEATURE_MASK_PKRU)
 extern u64 host_xcr0;
-
-extern u64 kvm_supported_xcr0(void);
+extern u64 supported_xcr0;
 
 extern unsigned int min_timer_period_us;
 
-- 
2.24.1